This invention relates to a fluorescent display device for graphic display which is adapted to display characters, numerals or the like by an elongated rectangular display section including a plurality of picture cells arranged longitudinally and laterally, and more particularly to a connection structure for such a fluorescent display device for electrically connecting the picture cells to each other.
A fluorescent display device for graphic display which includes a longitudinally or laterally elongated display section has been conventionally known in the art. The display section is formed of a plurality of longitudinally and laterally arranged picture cells into an elongated rectangular shape. For example, the display section may be formed of 24.times.264 picture cells arranged in a dot-like manner, resulting in carrying out display in eleven digits.
For example, a fluorescent display device of this type employs a single-matrix system to form and drive an electrode structure. In the single-matrix system, anode conductors for the picture cells of the display section are connected together in one of longitudinal and lateral directions of the display section to form a plurality of rows of picture cells parallel to each other, and a plurality of control electrodes are arranged above the display section in a manner to be perpendicular to the rows of picture cells, so that one of the rows of picture cells and control electrodes thus arranged is scanned and the other is fed with a display signal to carry out a desired selection of the picture cells.
Supposing that the display signal is supplied to the control electrodes for driving the fluorescent display device, the control electrodes are subject to static driving, resulting in a voltage being constantly applied to the control electrodes depending upon a manner of display. Unfortunately, this causes the control electrodes to be heated due to inflow of electrons thereto, leading to deformation of the control electrodes sufficient to adversely affect display. Also, this, in the worst case, causes the control electrodes to be electrically contacted with the anode conductors or other electrodes, resulting in short-circuiting. In order to avoid the problem, it has been generally carried out to scan the control electrodes and feed the rows of picture cells with the display signal.
In the conventional fluorescent display device described above, it would be considered that the control electrodes are formed into the same longitudinal dimension or length as a dimension of a long side of the display section and arranged in juxtaposition to each other in a direction of a short side of the display section. Such a construction permits the number of times at which the control electrodes are scanned to be decreased to increase a duty ratio when scanning the control electrodes. Unfortunately, this renders an arrangement of the control electrodes while stretching troublesome. In particular, this readily causes deterioration of quality of display and short-circuiting between the control electrodes and any other electrodes due to sagging and vibration of the control electrodes during the operation. Thus, in the conventional fluorescent display device, it has been generally carried out that the control electrodes are formed into the same length as a dimension of the short side of the display section and arranged in juxtaposition to each other in a direction of the long side of the display section, although such an arrangement causes a decrease in duty ratio.
Also, in the conventional fluorescent display device, filamentary cathodes are stretchedly arranged in the long side direction of the display section in order to ensure enlargement of a display area, simplification of wiring arrangement, reduction in energy consumption and the like. Supposing that the control electrodes are arranged in parallel with the filamentary cathodes under such conditions that the filamentary cathodes are arranged in the long side direction of the display section, scanning of the control electrodes causes positional relationships between the filamentary cathodes and the control electrodes to which a voltage is applied to be varied, leading to a failure in driving of the fluorescent display device under the same conditions. This is another reason that the control electrodes are arranged in the long side direction of the display direction.
For the reasons noted above, in the conventional fluorescent display device for graphic display which includes the elongated display section, the control electrodes are formed into the same length as the short side of the display section and arranged in the long side direction of the display section in a manner to be spaced from each other at predetermined intervals. The anode conductors for the picture cells of the display section are arranged perpendicular to the longitudinal direction of the control electrodes and connected together in the long side direction of the display section. The control electrodes are scanned and each row of anode conductors perpendicular to the control electrodes are supplied with a display signal, resulting in the desired display being obtained.
Unfortunately, the conventional fluorescent display device constructed as described above has a disadvantage of being increased in the number of control electrodes to be scanned, resulting in being decreased in duty ratio. For example, supposing that the display section is formed of 24.times.264 picture cells arranged in a dot-like manner, the duty ratio is decreased to a level as small as 1/264, so that the device fails to exhibit sufficient luminance unless a voltage applied to the anode conductors is increased. Unfortunately, an increase in driving voltage causes a driving IC used to be expensive and promotes deterioration of a phosphor layer.
Alternatively, a multi-matrix system may be used for constructing and driving the fluorescent display device including the elongated display section. The multi-matrix system permits each of the control electrodes to cover two rows of picture cells in the short side direction of the display section and the anode conductors to be connected together for each two or three picture cells. The system permits the duty ratio to be doubled, to thereby reduce the number of ICs required for driving the control electrodes to half, however, it causes the number of ICs necessary to control the anode conductors to be three or four times. Also, it causes the wiring arrangement to be complicated, resulting in application of the multi-matrix system to the picture cells which are arranged at small intervals being hard.